Selective material recovery from natural brines

ABSTRACT

Embodiments relate to methods for generating selected materials from a natural brine. A natural brine comprising at least a portion of a selected material is heated. CO2 is added and mixes with the natural brine forming a mixture such that the CO2/P is a first predetermined value. The mixture is held so that impurities in the natural brine precipitate as solids leaving a second brine substantially comprising the selected material. The second brine is heated. CO2 gas is injected into the second brine, mixing so that the CO2/P is a second predetermined value. The mixture is held so that the selected material precipitates out and are removed.

RELATION TO OTHER APPLICATIONS

This application claims priority benefit as a continuation of U.S.Non-Provisional patent application Ser. No. 16/537,985 filed Aug. 12,2019, currently pending, the entirety of which is incorporated byreference herein.

STATEMENT OF GOVERNMENT SUPPORT

The United States Government has rights in this invention pursuant to anemployer/employee relationship between the inventors and the U.S.Department of Energy, operators of the National Energy TechnologyLaboratory (NETL) and site-support contractors at NETL under ContractNo.: DE-FE0004000.

TECHNICAL FIELD

This disclosure relates to a method of generating selected materialsfrom a natural brine.

BACKGROUND

Natural geothermal brines are hydrothermal fluids heated by natural heatunder the earth's surface. Natural geothermal brines are considered anenvironmentally preferred and renewable energy source. These brinescontain materials leached from minerals while still underground. Thecurrent technology to generate materials from natural brines requires aseries of football field-sized evaporation ponds, lengthy leachingprocesses that consume time (approximately 18-24 months) and energy, andthat emit carbon dioxide (CO₂). During this evaporation, largequantities of diesel fuel are consumed producing carbon dioxide. Afterconcentration of the selected materials through evaporation, the brinesgenerally need to be transported a long distance to a processing plantthat generates the selected compounds by multiple carbonation steps.This carbonation process requires various solid additives, including:soda ash (Na₂CO₃), lime (CaO), hydrochloric acid (HCl), organic solvent,sulfuric acid (H₂SO₄), and alcohol. Several tons of the combinedadditives may be required to produce a ton of selected material in theseprocesses. Excluding land transit of the concentrated brine solutions,the current leading carbonation operation may consume more than 10GJ/ton of Li₂CO₃ produced (equivalent to a cost of $208/ton of Li₂CO₃production @ $0.07/kWh).

There is, therefore, a need for a method for generating selectedmaterials from natural brines that requires less time, energy, andproduction costs versus existing technology.

SUMMARY

In one aspect, a method for generating selected materials from a naturalbrine. Heating a natural brine in a vessel to a first predeterminedtemperature. The natural brine comprises at least a portion of aselected material. Adding CO₂ into the vessel whereby the CO₂ mixes withthe natural brine forming a mixture such that the CO₂/P (CO₂ mass over atotal pressure within the vessel) is a first predetermined value.Holding the mixture for a first predetermined time after the CO₂addition such that a solid is precipitated from the mixture. Separatingthe precipitated solid from the mixture, leaving a second brinesubstantially comprising the selected material. Heating the second brineto a second predetermined temperature. Adding CO₂ into the vesselwhereby the CO₂ mixes with the second brine forming a second mixturesuch that the CO₂/P is a second predetermined value. Holding the secondmixture for a second predetermined time after the CO₂ addition such thatthe selected material is precipitated from the second mixture. Removingthe selected material precipitate.

In another aspect, a method for generating selected materials from anatural. Heating a natural brine in a vessel to a first predeterminedtemperature. The natural brine comprises at least a portion of aselected material. Adding CO₂ into the vessel whereby the CO₂ mixes withthe natural brine forming a mixture such that the CO₂/P (CO₂ mass over atotal pressure within the vessel) is a first predetermined value.Holding the mixture for a first predetermined time after the CO₂addition such that a solid is precipitated from the mixture. Removingthe selected material precipitate.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the multipleembodiments of the present invention will become better understood withreference to the following description, appended claims, and accompanieddrawings where:

FIG. 1 is a schematic flow diagram illustrating the steps in accordancewith one embodiment of the present invention's process;

FIG. 2 illustrates a vessel used to treat a natural brine in accordancewith one embodiment of the present invention;

FIG. 3 illustrates CO₂ being added to a vessel in accordance with oneembodiment of the present invention;

FIG. 4 illustrates precipitates being separated from the natural brinein accordance with one embodiment of the present invention;

FIG. 5 illustrates selected material precipitates being removed from amixture in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1 , an embodiment of a method for generating selectedmaterials from a natural brine is illustrated and comprises eight steps.Heating 102 a natural brine in a vessel to a first predeterminedtemperature. The natural brine comprises at least a portion of aselected material. Adding 104 CO₂ into the vessel whereby the CO₂ mixeswith the natural brine forming a mixture such that the CO₂/P (CO₂ massover a total pressure within the vessel) is a first predetermined value.Holding 106 the mixture for a first predetermined time after the CO₂addition such that a solid is precipitated from the mixture. Separating108 the precipitated solid from the mixture, leaving a second brinesubstantially comprising the selected material. Heating 110 the secondbrine to a second predetermined temperature. Adding 112 CO₂ into thevessel whereby the CO₂ mixes with the second brine forming a secondmixture such that the CO₂/P is a second predetermined value. Holding 114the second mixture for a second predetermined time after the CO₂addition such that the selected material is precipitated from the secondmixture. Removing 116 the selected material precipitate.

In the illustrated embodiment, the first step is to heat 102 a naturalbrine in a vessel to a first predetermined temperature. In one or moreembodiments, the natural brine is sea water, saline water, freshwater,synthetic solutions, or industrial liquid waste containing the selectedmaterial. The natural brine comprises at least a portion of a selectedmaterial. A vessel is any hollow container used to hold a liquid. In oneor more embodiments the vessel is capable of holding a high pressurewithin the vessel, or is capable of holding a high temperature, or iscapable of holding a high pressure within the vessel and temperature. Ina preferred embodiment, the vessel is a pressure vessel. In one or moreembodiments, the first predetermined temperature is at least 200° C. Inother embodiments, the first predetermined temperature is equal to orgreater than 260° C. In an embodiment the selected material is lithium.In another embodiment, the selected material is a rare earth element orcomprises a rare earth element. In another embodiment, other desiredmaterials may be generated from a natural brine.

In the illustrated embodiment, the second step is adding 104 CO₂ intothe vessel. When the CO₂ is added to the vessel it mixes with thenatural brine forming a mixture. The mixture has a CO₂/P (CO₂ mass overa total pressure within the vessel) that is a first predetermined value.In an embodiment, the CO₂/P is greater than 6 g/atm. In anotherembodiment, the CO₂/P is greater than 18 g/atm. The mixture has theinherent properties including a pressure, temperature, and surfaceenergy. In one or more embodiments the pressure, temperature, andsurface energy are adjusted to recover the selected material. In otherembodiments, the CO₂ is added into the natural brine to form a mixturerather than prior art methods of pumping CO₂ into the brine.

As used herein, “adding” means CO₂ is introduced into the natural brinewith simultaneous adjustment of interior pressure within the vessel,which enables the control of the total pressure with respect to the massof CO₂, i.e., the CO₂/P ratio can be maintained at a constant targetedvalue when mixed. As used herein, prior art “pumping” of CO₂ causes apressure build up inside the vessel. Adding CO₂ to the natural brinewhile maintaining a first determined CO₂/P allows for the highestdissolution that can be strategically achieved for the selectedmaterial. This is shown through ratios of CO₂/P and by crossing overiso-pressure (constant pressure) contours in multiple dimensionsconsisting of all the parameters. Depending on the ratio of CO₂ to theCO₂ dissolved in the liquid, the effective CO₂/P can change. The presentinvention, unlike prior art methods, allows for a higher CO₂ mass insolution without increasing P, or lowering P without decreasing CO₂,which tactically enables discovery of required thermodynamic domainswhere the selected material is stable or unstable. This enables highrecovery rates of the selected material that are possible throughcontrol of the CO₂/P parameter ranges.

Preferably, CO₂ is added in a way to maximize the CO₂ reaction surfacearea with the natural brine. In one or more embodiments, reactions maybenefit from other properties such as surface tension and zetapotential. The CO₂ may come from natural, industrial, or waste sources.Natural brine treatment through CO₂ is preferential over prior artmethods because it is a low cost additive with known process controls.In an embodiment, the CO₂ is a gas. In another embodiment, the CO₂ is aliquid. In an embodiment, substantially all the CO₂ added to the vesselis retained within the natural brine. In another embodiment, only aportion of the CO₂ added to the vessel is retained within the naturalbrine.

If the CO₂ is introduced to the natural brine as small spheroids orbubbles (<10 μm in diameter), surface properties of the CO₂ such assurface tension and zeta potential would promote local concentrations ofOH⁻, which increases as the CO₂ spheroids decrease in size; i.e.,dissolution of CO₂ into the OH⁻-rich region near the CO₂/brine interfacefacilitates the local formation of HCO₃ ⁻. Ions of the selectedmaterials would be attracted to the negativity of the CO₂ surface, whichthen promote the formation of such compounds. In this case, thegeneration process may be operated at relatively low temperatures, suchas room temperature, and very low CO₂/P values, such as 0.01 g/atm,would be sufficient to facilitate the precipitation of select materials.

The third step is holding 106 the mixture for a first predeterminedtime. The first predetermined time begins after the CO₂ injection andlasts for the length of time necessary such that impurities in thenatural brine precipitate as solids. Preferably, the first predeterminedtime is greater than 20 minutes. This leaves the mixture substantiallycomprising dissolved selected material ions and dissolved chlorine ions.

In the illustrated embodiment, the fourth step is separating 108 theprecipitated solids from the mixture. In an embodiment, the solidprecipitate is impurities or byproducts. Separation is conducted with aseparation device that is used to divide solid precipitate impurities orbyproducts. In an embodiment, the separation device is any device thatis capable of separating solids from liquids such as a sieve. In anembodiment, the mixture is moved into a second vessel to complete thestep of separation 108. In an embodiment, the precipitated solids can berecycled or reused. In another embodiment, the precipitated solid is theselected material. In such embodiment, the method can continue tofurther separate selected materials from the mixture or stop.

In the illustrated embodiment, the fifth step is heating 110 the secondbrine to a second predetermined temperature. Embodiments include, thesecond predetermined temperature is at least 200° C. Other embodimentsinclude that the second predetermined temperature is at least 200° C. Inone or more other embodiments, the second predetermined temperature isequal to or greater than 260° C. In an example of another embodiment,the second predetermined temperature is equal to the first predeterminedtemperature.

In the illustrated embodiment, the sixth step is adding 112 CO₂ into thevessel. The CO₂ mixes with the second brine forming a second mixturesuch that the CO₂/P is a second predetermined value. In an embodiment,the CO₂/P is greater than 50 g/atm. Preferably, the CO₂/P is greaterthan 200 g/atm. In an embodiment, the CO₂ is a gas. In anotherembodiment, the CO₂ is a liquid. In an embodiment, substantially all theCO₂ added to the vessel is retained within the natural brine. In anotherembodiment, only a portion of the CO₂ added to the vessel is retainedwithin the natural brine.

If the CO₂ is introduced to the natural brine as small spheroids orbubbles (<10 μm in diameter), surface properties of the CO₂ such assurface tension and zeta potential would promote local concentrations ofOH⁻, which increases as the CO₂ spheroids decrease in size; i.e.,dissolution of CO₂ into the OH⁻-rich region near the CO₂/brine interfacefacilitates the local formation of HCO₃ ⁻. Ions of the selectedmaterials would be attracted to the negativity of the CO₂ surface, whichthen promote the formation of such compounds. In this case, thegeneration process may be operated at relatively low temperatures, suchas room temperature, and very low CO₂/P values, such as 0.01 g/atm,would be sufficient to facilitate the precipitation of select materials.

In the illustrated embodiment, the seventh step is holding 114 thesecond mixture for a second predetermined time after the CO₂ injectionsuch that chlorine is suppressed and remains as dissolved ions while theselected material ions precipitate out as a carbonate and issubstantially the only solid in the second mixture. Embodiments includethat the second predetermined time is at least 3 minutes. Exemplaryembodiments include that the second predetermined time is at least 20minutes. In other embodiments, the second predetermined time is equal tothe first predetermined time.

In the illustrated embodiment, the eighth step is removing 116 theselected material precipitate from the second mixture. Theoretically,recovery of the selected material is possible with a >99.0% purity. Inan embodiment the purity of the selected material recovered is greaterthan 50%. In prior art methods, pumping CO₂ into brines at atmosphericpressure is known to simply acidify the solution. This dissolves variousundesired materials into the solution and/or precipitate unwantedsolids, making the selected material recovery more complex (minimallycontrollable) and less pure.

Referring to FIG. 2 , according to an embodiment of the presentinvention, a vessel 202 having a pressure gauge is used for generatingselected materials from a natural brine 200. The natural brine 200 isheated from approximately 200 to 260° C. in vessel 202.

Referring to FIG. 3 , according to an embodiment of the presentinvention, CO₂ 304 is added to a vessel 302. The CO₂ 302 mixes with thenatural brine 306 to create a mixture 310 in such a way that CO₂/P>6g/atm or preferably CO₂/P>18 g/atm. The mixture 310 is held under theseconditions for first predetermined time. The first predetermined time,according to an embodiment, is approximately at least 3 minutes afterCO₂ injection, or preferably longer than 20 minutes. At this stage,untargeted elements (impurities or byproducts), including, but notlimited to K, Na, Ca, Mg, Ba, Fe, Al, and so on, from the brine,precipitate as solids while only selected material remain dissolved inthe mixture 310.

Referring to FIG. 4 , according to an embodiment of the presentinvention, within the vessel 402 the solid precipitates 406 areseparated from the mixture 410 using a separation device 408. The totalpressure within the vessel may be maintained until solid precipitate 406separation 408 is complete to minimize solid dissolution back into themixture 410. At this stage, the mixture 410 only substantially containsselected material ions.

Referring to FIG. 5 , according to an embodiment of the presentinvention, CO₂ 504 is added into the vessel 502 to be mixed with thesecond mixture 514 at 260° C. in such a way that CO₂/P>50 g/atm, orpreferentially >200 g/atm. The second mixture 514 is held under theseconditions for a second predetermined time of at least 3 minutes afterCO₂ 504 injection, or preferentially longer than 20 minutes. At thisstage, the selected material 512 precipitates out from the secondmixture 514.

Embodiments may be integrated into existing geothermal power plants.Existing geothermal power plants pump out brines for power generationfrom which selected materials can be generated. Additionally, theprocess generates excess heat while concentrating the selected materialand producing the selected material, which can be used for powergeneration.

Having described the basic concept of the embodiments, it will beapparent to those skilled in the art that the foregoing detaileddisclosure is intended to be presented by way of example. Accordingly,these terms should be interpreted as indicating that insubstantial orinconsequential modifications or alterations and various improvements ofthe subject matter described and claimed are considered to be within thescope of the spirited embodiments as recited in the appended claims.Additionally, the recited order of the elements or sequences, or the useof numbers, letters or other designations therefor, is not intended tolimit the claimed processes to any order except as may be specified. Allranges disclosed herein also encompass any and all possible sub-rangesand combinations of sub-ranges thereof. Any listed range is easilyrecognized as sufficiently describing and enabling the same range beingbroken down into at least equal halves, thirds, quarters, fifths,tenths, etc. As a non-limiting example, each range discussed herein canbe readily broken down into a lower third, middle third and upper third,etc. As will also be understood by one skilled in the art all languagesuch as up to, at least, greater than, less than, and the like refer toranges which are subsequently broken down into sub-ranges as discussedabove. As utilized herein, the terms “about,” “substantially,” and othersimilar terms are intended to have a broad meaning in conjunction withthe common and accepted usage by those having ordinary skill in the artto which the subject matter of this disclosure pertains. It should beunderstood by those of skill in the art who review this disclosure thatthese terms are intended to allow a description of certain featuresdescribed and claimed without restricting the scope of these features tothe exact numerical ranges provided. Accordingly, the embodiments arelimited only by the following claims and equivalents thereto.

We claim:
 1. A method for extracting selected material carbonate from abrine, the method comprising the steps of: a. pumping CO₂ gas bubblesinto a brine at ambient temperature and pressure whereby the CO₂ gasbubbles mix with the brine, thereby generating a CO₂ brine; b. preparinga second brine comprising a selected material; c. mixing the CO₂ brinewith the second brine at an ambient temperature and pressure therebyforming a resultant mixture; d. precipitating a selected materialcarbonate from the resultant mixture; and e. removing the selectedmaterial carbonate precipitate.
 2. The method of claim 1, wherein thestep of generating the CO₂ brine further comprises controlling number ofCO₂ bubbles, size of CO₂ bubbles, pH, stirring, aeration, agitationtemperature, and pressure.
 3. The method of claim 1, wherein the step ofpreparing the second brine further comprises controlling temperature,volume, seed, and pH.
 4. The method of claim 1, wherein the step ofmixing the CO₂ brine with the second brine further comprises controllingvolume ratio of the CO₂ brine and second brine and stirring.
 5. Themethod of claim 1, wherein the resultant mixture is further conditionedby controlling holding time, temperature, and pressure.
 6. The method ofclaim 1, wherein the selected material carbonate precipitate comprisesat least one of a rare earth element, lithium, gold, iron, copper, andmagnesium.
 7. The method of claim 1, wherein the selected materialcarbonate precipitate is lithium carbonate.
 8. The method of claim 1,wherein the resultant mixture is further concentrated by one or more oftop pouring, skimming, or drying.
 9. The method of claim 1, wherein thestep of removing the selected material carbonate precipitate from theresultant mixture comprises using at least one of a filter, gravity,centrifuge, and scraping.
 10. The method of claim 1, wherein the CO₂ gasbubbles have a diameter, wherein said diameter is ≤200 nm.
 11. Themethod of claim 1, wherein the pH of the CO₂ brine is ≤5.5.
 12. Themethod of claim 1, wherein the pH of the second brine is ≤8.
 13. Themethod of claim 1, wherein the resultant mixture formed by mixing theCO₂ brine with the second brine is in a volume ratio of 1.5:10 CO₂ brineto second brine.
 14. The method of claim 1, wherein the brine is ageothermal brine.
 15. The method of claim 1, wherein the brine is aproduced water from oil and gas industries.
 16. The method of claim 1,wherein ambient temperature is room temperature and ambient pressure isapproximately 1 atm.
 17. A method for extracting selected materialcarbonate from a brine, the method comprising the steps of: a. pumpingCO₂ gas into a brine at ambient temperature and pressure whereby the CO₂gas bubbles mix with the brine, thereby forming a resultant mixture,wherein the brine comprises a selected material that reacts with the CO₂gas to form a selected material carbonate; b. precipitating the selectedmaterial carbonate from the resultant mixture; and c. removing theselected material carbonate precipitate.
 18. The method of claim 17, inwhich the step of mixing further comprises at least one of a batch and acontinuous process.
 19. The method of claim 17, wherein unreacted CO₂gas is cycled back into the resultant mixture.
 20. The method of claim17, wherein the pumping, precipitating, and removing the selectedmaterial carbonate precipitate occurs underground.